[X86]: Updated r272801 to promote 16 bit compares with immediate operand

to 32 bits. This is in response to a comment by Eli Friedman.

llvm-svn: 272814

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 198b48fe9d4..2dc71f100d0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3927,6 +3927,26 @@ bool X86::isCalleePop(CallingConv::ID CallingConv,
   }
 }
 
+/// \brief Return true if the condition is an unsigned comparison operation.
+static bool isX86CCUnsigned(unsigned X86CC) {
+  switch (X86CC) {
+  default:
+    llvm_unreachable("Invalid integer condition!");
+  case X86::COND_E:
+  case X86::COND_NE:
+  case X86::COND_B:
+  case X86::COND_A:
+  case X86::COND_BE:
+  case X86::COND_AE:
+    return true;
+  case X86::COND_G:
+  case X86::COND_GE:
+  case X86::COND_L:
+  case X86::COND_LE:
+    return false;
+  }
+}
+
 static X86::CondCode TranslateIntegerX86CC(ISD::CondCode SetCCOpcode) {
   switch (SetCCOpcode) {
   default: llvm_unreachable("Invalid integer condition!");
@@ -14746,6 +14766,17 @@ SDValue X86TargetLowering::EmitCmp(SDValue Op0, SDValue Op1, unsigned X86CC,
 
   if ((Op0.getValueType() == MVT::i8 || Op0.getValueType() == MVT::i16 ||
        Op0.getValueType() == MVT::i32 || Op0.getValueType() == MVT::i64)) {
+    // Only promote the compare up to I32 if it is a 16 bit operation
+    // with an immediate.  16 bit immediates are to be avoided.
+    if ((Op0.getValueType() == MVT::i16 &&
+         (isa<ConstantSDNode>(Op0) || isa<ConstantSDNode>(Op1))) &&
+        !DAG.getMachineFunction().getFunction()->optForMinSize() &&
+        !Subtarget.isAtom()) {
+      unsigned ExtendOp =
+          isX86CCUnsigned(X86CC) ? ISD::ZERO_EXTEND : ISD::SIGN_EXTEND;
+      Op0 = DAG.getNode(ExtendOp, dl, MVT::i32, Op0);
+      Op1 = DAG.getNode(ExtendOp, dl, MVT::i32, Op1);
+    }
     // Use SUB instead of CMP to enable CSE between SUB and CMP.
     SDVTList VTs = DAG.getVTList(Op0.getValueType(), MVT::i32);
     SDValue Sub = DAG.getNode(X86ISD::SUB, dl, VTs,